Conversion of paraffins to aromatics



CONVERSION OF PARAFFINS To AROMATICS FiledDec. 1, 1959 FEsn 2 Sheets-Shet. 1

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' 64 )66 I 74 AROMATYICS I HF CARBON I STILL REACTOR I 73 EXTRACTION F68 I J TO FUEL OR DEALKYLATION,

' HYDROGENATION,

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Henry G eorge Ellerf Feb; 27,- 19 2 Filed Deb. 1, 1959 s-Sheet 2 Bm mE PH e msm mmma mm mzmmommx 5:530 :21

momwummzou w mv omx Sum SEm zouz: 586ml Henry George Eller'r Charles Newton KimberlimJr. lnvemorsv primarily to tar' and isobutane. produced and the tar product is best described as a con- 3,023,157 CONVERSIGNOF PARAFFENS T AROMATICS Henry George Eiiert and Charles Newton Kimberlin, Jr., Baton Rouge, La, assignors to Essa Research and Engineering Company, a corporation of Delaware Filed Dec. 1, 1959, Ser. No. 856,392 11 Qlain'rs. (Cl. 2864) The present invention relates to the conversion of hydrocarbons, particularly those boiling in the gasoline and naphtha boiling range, to more valuable aromatics con taining compositions. More particularly, the present invention relates to the catalytic conversion of hydrocarbon streams into highly aromatic streams with a hydrogen fluoride catalyst.

The conversion of hydrocarobns with hydrogen fluoride is a well-known reaction. It is normally carried out in the liquid phase, either with the aqueous or the anhydrous acid and with or without catalyst promoters such as BF to give a variety of products, mostly polymers or isomers. Aromatics, however, are not generally formed to any significant extent.

It is, of course, highly desirable to convert low octane hydrocarobns, such as virgin naphthas, into high octane aromatics containing material. It is also highly advantageous to provide means for synthesizing high density fuels suitable for jet engines; these boil in the keroseneheavy naphtha and kerosene range. Furthermore, in the near future, automotive octane requirements will require the reprocessing of catalytic naphthas; i.e., naphthas produced by catalytic cracking of gas oils. These materials have poor qualities due to their high olefinicity and consequent poor leaded motor octane number.

It is the principal object of the present invention to set forth a novel process for converting parafiinic hydrocarbons into aromatic hydrocarbons in good yields and with little secondary reaction by-product.

It is still a further object of the present invention to set forth a novel process for converting certain light, low value hydrocarbons into valuable fuel products boiling in the middle distillate range.

It is still further an object of the present invention to raise the aromatic content of hydrocarbons or convert non-benzenoid hydrocarbons to aromatics by a novel process making little or no coke.

Other objects and advantages of the present invention will appear as the description proceeds.

it has now been found that these objectives may be achieved by contacting hydrocarbon streams of the nature hitherto described in the vapor phase with vaporized hydrogen fluoride in the further presence of a high surface Biff GilifWiST ii'iilf contacting agent at elevated fe'ffifiiw ture. The reaction is carried out at a temperature of about 600? to 1300 F., preferably 7 Q to 1150 F., and the preferred contacting agent is high surface area char or other carbon. In the absence or the'h'ig'h surface area support, substantial-lyno reaction isobtained, while in the presence of the carbon, highly aromatic materials are obtained, whose nature depends uponthe composition of the feed.

The distinction between this conversion techniqueand that Oi: conversion by 'ffefifig' with liquid is best 1111 ders'tood by considering the conversion of a light virgin naphtha which contains benzene and appreciable amounts of naphthefies. This feed is converted'to an aromatic, 180 F.+ product-and a (2 gas product by treating at elevated temper-attire with HF vapor in the presence or activated carbon. Little if any coke is produced and the gas product consists mainly of C olefins and paraffins. In contrast, liquid HF converts the same feed No olefinic gases are 2 junct polymer consisting of high molecular Weight cyclic olefins and dienes.

The conversion of normal heptane by the two catalysts further distinguishes the vapor phase HF catalyst from the liquid HF catalyst. With the HF vapor-carbon system, the heptane feed is converted to gas and aromatics. The gas contains mainly normal butane and propane as well as lesser amounts of ethylene, propylene and methane. The liquid product consists almost exclusively of C to C and other substituted benzenes. In contrast, conversion by the liquid catalyst gives primarily isobutane, isopentane and some isohexanes. No aromatics and no olefinic gases are obtained. In this case, hydrogen balance is maintained through the production of unsaturated conjunct polymer. V

The selectivity of the HF vapor/ carbon system for aromatics production is somewhat surprising in view of the fact that liquid HF, vapor HF and carbon individually show no aromatization activity. In comparison with standard aromatization techniques, the vapor HF/carbon process shows unique advantages in that (l) paraifins from pentane through cetane and even heavier are .all readily converted to similar, aromatic products, (2) the catalyst system is relatively insensitive to the normal catalyst poisons, and (3) hydrogen pressure is not required for selective conversion.

Although any mixture of hydrocarbons may be treated in accordance with the present invention, the present 'diesel fuel; and FIGURE 3, an embodiment for, maximizing aromatics from a naphtha reforming operation;

Turning now to FIGURE 1, a feed of the type described above is passed through line 2', vaporized in heater 4 and the heated vapor passed into reaction vessel 6. Similarly, gaseous hydrogen fluoride is passed via line 8 into reactor 6. The latter is packed with highly porous, non-reactive contacting agent, preferably activated carbon. By non-reactive is meant those agents that will not react with HF. Besides carbon, amorphous calcium fluoride, magnesium fluoride and similar compositions may also be employed. The hydrogen fluoride to hydrocarbon feed' ratio is about-0.1 to 4.0, preferably 0.5 to 2. The liquid hourl space velocity is maintained at from 0.2 to 4.0 v./v., depending upon the temperature and the acid to' oilratid. The temperature'within reactor 6 may be from 600 to about 13'00 and preferably 750 t0 1150' F. Pre'SSu'i'e iS atmospheric 61" slightly above. Thus with the lighter feeds, temperatures may be from 850 to 1150 F., while 750 to 1050 F. is preferable for the heavier naphthas.

The reactionmixture comprising reactants, catalyst and reactor products is passed via line It} to condensation vessel 12. Any low molecular weight hydrocarbon gases formed during: the reaction, C and lower, may be recycled to the reactor via line 14. This recycle has the effect of decreasing dry gas make in the reaction. Similar efiects may be realized by recycling a portion of the desired aromatc hydrocarbon product;

The condensed product may then be passed to settler 18 via line 16. may then be separated and recycled via line 20 and be revaporized. The desired aroma-tized product is recovered via line 22 and may be freed from acid contaminants by washing, caustic scrubbing, and the like, followed by a distillation step.

The embodiment shown in FIGURE 2 is especially attractive for use in many areas where virgin naphtha is in over-supply while heavier fuels, particularly jet and diesel fuels are in high demand. In accordance with this embodiment, the aromatic fuel produced in the reaction is subsequently hydrogenated, preferably in part at least by the hydrogen formed during the reaction, to improve the burning characteristics and produce a high quality, high density diesel or jet fuel.

Turning now to FIGURE 2, a naphtha feed, which may be virgin, catalytic, or thermal is passed via line 30 into reactor 32, packed with active carbon. Hy drogen fluoride is admitted via line 58. Reaction conditions within 32 are temperatures of 700 to 1200 F., hydrocarbon space velocity of 0.5 to 2 v./v./hr., 0.1 to 2.0 I-IF/oil ratio (weight) and a pressure of atmospheric to 400 psi". It is to be understood that the more severe of these conditions are used in processing saturated, virgin naphthas, while less severe conditions are used with reactive thermal or catalytic naphthas. Further, when elevated pressures are employed, somewhat ,more severe reaction conditions are employed to otfset the retarding effects of pressure on reaction rates. High pressures are, however, beneficial in another respect as indicated below.

The reactor efiluent is then passed via line 34 to partial condenser 36 where products heavier than the feed are withdrawn via line 38 and passed to hydrogenation zone 40. The remainder of the reactor effiuent is withdrawn through line 42, condensed, and passed to settler 44. Unconverted feed and some lower hydrocarbons are recycled to reactor 32 via line 48. A hydrogen-rich stream is withdrawn overhead from settler 44 and, in the case of a previous high pressure operation in reactor 32, it is passed directly to hydrogenator 40 via lines 54 and 55. If a low pressure operation is employed in 32, the hydrogen-rich stream may be passed via line 48 to compressor 50 for compression up to 200 to 400 p.s.i.g. From settler 44 acid is recycled to the reactor via line 46.

The heavy aromatic product from the reactor, which may boil in the range of 200 to 600 F., is then recombined with the hydrogen at, for example, 200 to 400 p.s.i.g. and 500 F., using a platinum catalyst, in

hydrogenator 40. which is of conventional design. and a high quality product boiling in the kerosene range is recovered. If desired or necessary, auxiliary or supplementary hydrogen may be supplied through line 57.

In FIGURE 3 there is shown an embodiment for maximizing the aromatics content of fuels resulting from catalytic cracking or reforming of naphthas. These materials contain'appreciable amounts of low octane components such as parafiins, olefins and naphthenes. The conversion of these components to aromatics would result in the production of blending streams of much higher quality.

In accordance with the embodiment shown in FIGURE 3, a reformate containing substantial amounts of aromatic'and naphthenic components as well as lower octane components consisting of paraflins is separated into an aromatics concentrate and a non-aromatics concentrate.

This separation is achieved by any well-known means;

solvent extraction is particularly useful. Thus a feed,

which may be a 200 F.+ reformate or a total reformate or a heavy catalytic naphtha or a total catalytic naphtha is passed via line 60 into extraction zone 62. Fresh solvent selective for aromatics, such as liquid S furfurahdiethylene glycol, phenol or the like, is passed into the extraction zone through lines 61 and 60. Under conventional extraction conditions, the aromatic constituents are extracted from the hydrocarbon feed. The ratfinate consisting of low octane, mainly parafiinic hydrocarbons, is passed via line 64 to the aromatization unit 66 of the type and nature previously disclosed, and operated under elevated temperatures and vapor phase 4 conditions in the presence of active carbon and hydrogen fluoride.

The reactor effluent is withdrawn through line 67, freed from light gases and passed to still 70. Overhead is withdrawn an HF stream which is recycled to reactor 66. The desired aromatic fraction is withdrawn through line 74 and consolidated with the aromatic extract from 62, providing a highly aromatic high octane blending stock. Still bottoms, withdrawn through line 78, are suitable for fuel or may be dealkylated or hydrogenated.

The process of the present invention may be subject to many variations obvious to those skilled in the art. Thus the embodiment shown in FIGURE 3 may be varied by carrying out the catalytic reforming of naphtha to a relatively low conversion level, followed by distilling the product, segregating the fraction boiling up to' about .250" F. and treating this fraction with the HF and active carbon. The bulk of the aromatics formed in the reforming operation are thus excluded in this fraction fed to the aromatizer.

- Though the process has been described in connection with a vfixed bed of contacting agent, the latter may be resent in the form of a bed of finely divided fluidized solids, or a moving bed, or even a slurry. Furthermore, it may be desirable to add a promoter to the active carbon. Suitable promoters are group II, III and VIII metals, metal oxides and metal fluorides, in concentration of 0.1 to 20 wt. percent of the carbon. Similarly, it may be desirable to add promoters to the hydrogen fluoride, such as BF small amounts of water or both.

The carbon gradually loses activity and selectivity with time, and reactivation is required. The latter may be accomplished by feeding superheated steam continually or intermittently to the carbon bed. While this may be done in a'single vessel system, best results are obtained in a two vessel system such as employed in conventional fluid solids units. In this case, reaction is carried out in one vessel, regeneration in the other at somewhat higher than process temperatures; e.g. 1400 to 1600 F. as against 800 to 1000 F.

The advantages of operating in accordance with the present invention may be further seen and illustrated by the following specific examples.

EXAMPLE 1 (a) A mixture of 2.9 parts of anhydrous HF and 1 part by weight of normal dodecane were passed through an empty Monel tube at 0.4 total hourly space velocity and 920 F. Less than 5% conversion to gas was obtained and the recovered liquid was essentially pure dodecane.

(b) Similar experiments were made with dodecane feed in which the reactor was packed with Monel gauze and copper shot.

Packing Monel Copper gauze shot 962 951 1. 3 1. 5 Total v./v. 0.7 0.8 Conversion, weight percent- 5 5 Again negligible conversion was obtained and the recovered liquid was essentially uncon'erted dodecane.

(c) A mixture of 1.5 parts of anhydrous HF and 1 part by weight of n-dodecane were passed at 960 F. and 0.8 total hourly space velocity over cc. of activated car- ,bon /s" pellets; surface area, 1062 m. /g.; pore volume, 0.68 cm. /g.). Complete conversion of the feed was obtained. Of the products, 36% was gas consisting primarily of normal butane, propane, methane, and hydrogen with lesseramounts of light olefins. The liquid product, obtained in 64% yield, consisted almost exclusively of C to C aromatics, predominantly substituted benzenes. No measurable amount of coke or tar was produced. After repeated experiments over the same charge of activated carbon, little change in surface properties was indicated.

(d) For the purpose of comparison, normal cetane (a C paraflin very similar in properties to dodecane) was treated for 2 hours at 350 F. with 0.9 wt. of anhydrous, liquid HP. The experiment was carried out in a stirred Monel autoclave under the developed pressure of the system. About 55% conversion was obtained. The C yield was 34.8% and consisted chiefly of isobutane and isopentane. No light olefins were obtained. A 3.8% yield of liquid product (excluding cetane), containing less than aromatics was also obtained. The remaining product was a heavy black tar, obtained in 16.4% yield, and consisting of complex, high molecular weight cyclic olefins and dienes and showing the characteristics of a typical conjunct polymer.

(e) As a further comparison, normal cetane was cracked over activated carbon, in the absence of HF at 935 F. and 1 v./v./hr. Conversion was 93%. Gas yield was 36.6% (on feed) while the yield of aromatics was only 11.4 wt. percent on feed.

EXAMPLE 2 Effect of HF on Conversion of Parafiins Over Activated Carbon Feed Heptane Dodecane Cetane Temperature, F 960 960 935 HF/Oil weight ratio 1. 3 1. 3 0 Total v./v.lhr 0.6 0.6 1.0 Conversion, weight perce 55 100 93. 3 Yields, weight percent:

05- 17 36 36. 6 Aromatics 38 64 11. 4

The aromatics obtained from heptane and dodecane using the HF/carbon catalyst are primarily substituted benzenes containing from 7 to carbon atoms. Trace amounts of aromatics up to molecular weight 300 are also formed. With activated carbon catalyst, the majority of the aromatics contain 10 to 12 carbon atoms, and no materials heavier than feed are present.

EXAMPLE 3 Efiect of HF in the Conversion of Heavy Naphtha It will be noted that, in the absence of HF, the activated carbon produces substantially no product, aromatic or otherwise, boiling in the middle distillate range.

EXAMPLE 4 The utility of the process for upgrading and converting various refinery streams into high value middle distillate product of high aromatic content is shown in Tables I and 11 below. In Table I there is detailed the nature of the feeds processed in accordance with the present invention and in Table 11 there is presented the yields.

In the example, A is a light C /C virgin naphtha boiling in the range of 140 to 185 F., B is a heavier virgin A B C D Mierodistillationz' Initial at F 143 228 121 259 50% 152- 272 232 358 188 366 332 395 Gravity, API 75.2 53.2 60.6 41. 7 Composition, vol. percent: 7

Paraflins 73.0 44. 5 19. 5 31.9 Olefins 1.0 51.2 23. 0 Naphthenes 22.0 36. 2 7. 5 11. 8 Ar0matics 5. 0 18. 3 11.8 33.3 Bromine number 92. 8 30. 5

TABLE II Naphtha COHVEISZOH Over HF Carbon [100 cc. charge activated carbon Feed A B O O D Temperature, F 999 993 886 998 995 HF/oil Weight ratio 1. 28 1. 41 1.41 1. 31 1.10 Total v./v./hr 2. 29 2.08 2. 26 2. 20 2. 38 Run length, minutes 60 60 60 60 60 Conversion, weight percent. 61. 8 30. 7 51.1 55. 2 68. 2 Yields, weight percent on feed (output):

2. 7 1.3 2. 6 1. 4 0.1 1. 6 1. 5 3. 3 1. 4 2.1 1.0 1.9 0.9 0.2 0.2 1. 5 1.9 1. 2 0.6 Ct to feed initial 2. 0 2. 6 Hea ier than feed 17. 6 57. 4 Coke 1. 3

. 6 naphtha boiling in the range of 230 to'350" F.,' C is a light catalytic naphtha, and D is a heavy catalytic naphtha.

TABLE I Feed Inspections 1 Columbia activated carbon,

What is claimed is:

1. A process for raising the aromatics content of hydrocarbon streams which comprises contacting said stream in the vapor phase in a conversion zone at a temperature of from about 600 to about 1300" F. with vaporized hydrogen fluoride in the presence of a high surface area contacting agent substantially inert to hydrogen fluoride.

2. A process for raising the aromatics content of by drocarbon streams which comprises maintaining at about 600 to 1300 F. an activated char and contacting a vaporized hydrocarbon stream and vaporized hydrogen fluoride with said char.

3. A process for aromatizing a naphtha stream which comprises contacting a vaporized stream of said naphtha in a reaction zone with vaporized hydrogen fluoride at a temperature of about 600 to about 1300 F. and at pressures from atmospheric to about 400 p.s.i.g. with high surface area activated carbon, and recovering a product of high aromaticity.

4. The process of claim 3 wherein the HF to oil ratio is in the range of 0.1 to 4.0.

5. The process of claim 3 wherein a boron fluoride promoter is passed to said reaction zone.

6. The process of claim 3 wherein a promoter selected from the class consisting of group II, III and VIII metals, oxides and fluorides, is present in said reaction zone.

7. The process of claim 3 wherein said activated car bon is periodically reactivated by feeding superheated steam to a bed thereof.

8. An improved process for converting naphthas into high quality middle distillate fuels of high aromatic content which comprises contacting a vaporized stream of said naphtha with vaporized HF and activated carbon at a temperature of about 700 to about 1200 .F. and pressure of atmospheric to about 400 p.s .i.g. in a reaction zone, withdrawing an aromatic product stream boiling in the middle distillate range, withdrawing a hydrogen rich stream, passing both said streams to a hydrogenation zone, and hydrogenating said aromatic product at least in part with hydrogen produced in the process.

9. The process of claim 8 wherein said aromatic comprising product withdrawn from said first named zone boils in the range of about 200 to 600 F. p

10. An improved process for maximizing the aromatics content of fuels resulting from catalytic and thermal hydrocarbon conversion processes which comprises segregating the aromatic and non-aromatic components of said fuels, subjecting the non-aromatic fraction to a vapor phase aromatization reaction in the presence of vaporized HF and activated carbon at a temperature of from about References Cited in the file of this patent UNITED STATES PATENTS 2,431,549 Frey Nov. 25, 1947 2,767,124 Myers Oct. 16, 1956 2,890,997 Hirschler June 16, 1959 

8. AN IMPROVED PROCESS FOR CONVERTING NAPHTHAS INTO HIGH QUALITY MIDDLE DISTILLATE FUELS OF HIGH AROMATIC CONTENT WHICH COMPRISES CONTACTING A VAPORIZED STREAM OF SAID NAPHTHA WITH VAPORIZED HF AND ACTIVATED CARBON AT A TEMPERATURE OF ABOUT 700* TO ABOUT 1200*F. AND PRESSURE OF ATMOSPHERIC TO ABOUT 400 P.S.I.G. IN A REACTION ZONE, WITHDRAWING AN AROMATIC PRODUCT STREAM BOILING IN THE MIDDLE DISTILLATE RANGE, WITHDRAWING A HYDROGEN RICH STREAM, PASSING BOTH SAID STREAMS TO A HYDROGENATION ZONE, AND HYDROGENATING SAID AROMATIC PRODUCT AT LEAST IN PART WITH HYDROGEN PRODUCED IN THE PROCESS. 